Check this out on How to replace color in photoshop CS2.
This following steps demonstrate how you can replace the color of the sky to other blue.

1. Open your image in Photoshop, select Image, Adjustments and select Replace Color.
(IMG:http://i3.photobucket.com/albums/y60/photoexpress/Documents/Replace%20Color/1.jpg)


2. Under Selection section, click on Eyedropper Tool and select the color to be replaced from the image.
(IMG:http://i3.photobucket.com/albums/y60/photoexpress/Documents/Replace%20Color/2.jpg)


3. Click on the Add-To-Sample icon (Eyedropper with the + sign), click on other tone to be replaced from the image.
(IMG:http://i3.photobucket.com/albums/y60/photoexpress/Documents/Replace%20Color/3.jpg)


4. Under the Replacement section, click on the Result Color box.
(IMG:http://i3.photobucket.com/albums/y60/photoexpress/Documents/Replace%20Color/4.jpg)


5. Select the color you want by moving the slider or using the circle color icon. Notice the image will preview instantly.
(IMG:http://i3.photobucket.com/albums/y60/photoexpress/Documents/Replace%20Color/5.jpg)


6. If you are happy with the color, click OK button to save the changes and here is the final result.
(IMG:http://i3.photobucket.com/albums/y60/photoexpress/Documents/Replace%20Color/6.jpg)


Enjoy PPing

Cheers! PhotoExpress.

Nice technique. Do u mind if i move it to the Article section?

Hmm, That's a good one
Thanks Bobby

Article section? Thought Photoshop technique?
I'm fine with the movement. Thanks.

thanks bro..have try it out..